In recent years, extensive concern has been directed at the presence of pollutants and contaminants in air and water. Various studies confirm the hazards to humans of such contaminants, and recent legislation has set stricter controls and regulations concerning, for example, the emission of contaminants into the atmosphere. These regulations, for the most part, are directed at rigidly controlling the concentration of the pollution within specified limits. The economic impact of meeting such regulations has been severe, and, in many cases, difficult or impossible with existing production or processing equipment.
Available methods of eliminating air toxics and volatile organic compounds (VOCs) are extremely expensive, particularly when the VOCs and air toxics are present in low concentrations. Thermal incineration is relatively difficult and expensive. While catalytic incineration does not require temperatures as high as thermal incineration, its performance is substantially degraded and unsatisfactory when applied to emission streams of low concentrations. Another method for treating air toxics and VOCs is through adsorption, utilizing a material such as activated carbon. After adsorption over a period of time, the VOCs and air toxics can be desorbed at a higher concentration through regeneration of the sorbent. However, while this procedure may effectively collect VOCs and air toxics, subsequent disposal of the adsorbed toxic components still presents problems. Other methods such as the use of ozone as an oxidizing agent are known and used, as is exposing a contaminated gaseous stream to ultraviolet light in the presence of oxygen and/or ozone such as taught, for example, in U.S. Pat. No. 4,045,316.
While the methods described above can be used in the control or destruction of VOCs and air toxics, they are particularly inefficient and costly where the VOCs and air toxics (hereinafter referred to as contaminants) are present in low concentrations. Low concentrations of contaminants make it inefficient and/or impractical to treat the large fluid volume involved in a reaction chamber as in the aforesaid U.S. Pat. No. 4,045,316 because the volumetric requirements for such reaction chambers become extremely large.
As a result, the problem of effectively treating or controlling contaminants in fluids, particularly where the concentration of the contaminants is low has not been satisfactorily solved by existing methods and apparatus. Moreover, in addition to the need for a low-cost and effective method of controlling contaminants in fluids, it is highly desirable that such a method be applicable to existing production equipment, production processes and waste incinerators since it has become necessary to retrofit and modify such existing equipment to meet the more demanding and stringent governmental regulations such as Titles I and III of the 1990 Clean Air Act Amendments. Moreover, it is important to minimize the amount of power required to control such contaminants, not only from a cost-effective point of view, but also because the generation of electric power frequently involves the burning of fossil fuels which leads to further emissions of contaminants into the atmosphere with the problem of controlling those contaminant emissions. Still further, it is important to avoid the generation of toxic materials by the control equipment such as results from the use of an adsorption process. That is, it is desirable that the contaminants be transformed or broken down into non-toxic compound and materials which can be readily disposed of.